The present invention relates to surface finishing pads and, more particularly, to an improved support and backing for the finishing medium of a tufted fiber rotary finishing pad.
Surface finishing pads of tufted fiber construction, used for buffing and polishing a variety of surfaces, are well known in the art. Most typically, these pads are circular in shape and are driven by a rotary buffing machine in which the pads are mounted thereon by use of any of several devices, including threaded connectors and hook and loop fasteners.
Pads using a soft fiber finishing medium commonly use wool yarn, but other synthetic fiber yarns, used alone or blended with wool, are also used. The fiber yarns are typically attached to a stiff, but flexible, base or backing layer by utilizing well known tufting methods and apparatus. Such tufted pads provide a number of distinct advantages in certain surface finishing operations over, for example, open cell polyurethane foam pads. However, tufted finishing pads have a number of deficiencies, most of which relate to the underlying supporting base or backing for the tufted fibers, which backing also provides the interface for attachment to the buffing machine.
The finishing pad support or backing must be rigid enough to retain the pad shape, yet flexible enough to provide some cushioning effect during operation. The industry has generally adopted a laminated construction for the backing used to support tufted fiber finishing media. The backing should be resistant to moisture and water-based cleaning solutions, tough enough to withstand perforation and stitch tear-out during operation, and formable into a curved peripheral edge which will hold its shape during use. One common prior art backing comprises a layer of polyester film laminated between two layers of a woven jute fabric. The jute layers help lock the tufted fabric in place and the polyester layer provides shape retention. In addition, a further polyester backing layer is laminated to the jute surface opposite the tufted face to allow the pad to be heat formed with a circular peripheral edge, as is common in the industry. Unfortunately, jute is not particularly durable, swells in the presence of moisture, and may capture and hold finishing compound in use. An alternate media support and backing utilizes a base laminate comprising a non-woven polyester layer and a solid film of polyester fabric material. The tufted fabric may be first applied to the non-woven layer and the polyester film laminated to the sewn non-woven layer and formed with a curved peripheral edge, if desired. Polyethylene is a commonly used polyester material, but other plastic resin backing and support materials are also utilized. These layered polyester laminates, though somewhat more resistant to water than jute, still soften and lose their shape in use. In addition, these materials do not provide sufficient strength to prevent perforation and stitch tear-out as a result of the high shear forces incurred in use.
A further problem, common to all prior art tufted pads, is the tendency of the fibers to separate from the backing at the peripheral edge of the pad during use. Attempts have been made to add additional reinforcing strips to the edge, and to bond the radially outermost fibers to the backing along the edge. However, prior art backing materials have not proved to provide a satisfactory bond for wool or synthetic fibers, and added reinforcing strips increase the pad cost without providing cost-effective benefit.